Having used both OSB and plywood sheathing on multiple home projects, I can honestly say each material has its place. When I built a garden shed a couple of years ago, I went with OSB due to the lower cost. It worked well for the short-term project, but I had to be diligent about sealing it and applying a moisture barrier.
On the other hand, when I helped my brother renovate his kitchen, we used plywood for the subfloor. The space was prone to spills and high humidity, and we knew that plywood would hold up better over time. Sure, it cost more, but it was worth the peace of mind knowing it would last longer in that environment.
Introduction
When it comes to building or renovating a home, one of the important decisions you’ll face is choosing the right sheathing material. Whether you’re working on a roof, walls, or floors, sheathing is crucial for creating a strong and durable structure. The two most common options are OSB (Oriented Strand Board) and plywood sheathing. But how do you decide which one is right for your project? Let’s break it down!
What is OSB?
OSB (Oriented Strand Board) is a type of engineered wood made by multiple layers of wood strands, typically fastened with adhesives. These strands are laid out in a specific orientation to give the board strength and stability. The result is a strong, versatile, and affordable material commonly used for subfloors, wall sheathing, and roof decking.
OSB is a favorite among contractors because of its affordability and availability. Its consistent thickness and size make it ideal for large-scale projects, and it’s often seen as a cost-effective alternative to traditional plywood.
What is Sheathing?
Sheathing refers to the layer of boards or panels that are fastened to the exterior studs, joists, or rafters of a building. It acts as a foundation for applying external finishes such as siding or roofing materials. Sheathing materials come in various forms, including plywood, OSB, foam board, and metal sheets, but for this article, we will focus on plywood sheathing as it’s the most common counterpart to OSB.
Key Differences Between OSB and Sheathing
At first glance, OSB and plywood sheathing may seem interchangeable, but there are some critical differences. These differences can affect your project in terms of cost, performance, and durability.
1. Composition
- OSB is made of wood strands and resin, while plywood is made by layering thin sheets of wood, glued together with alternating grain direction.
2. Appearance
- OSB has a unique look with visible wood strands, while plywood has a more uniform, polished appearance due to its layered construction.
3. Strength
- While both are strong materials, OSB tends to be denser, giving it a slight edge in strength in some cases, especially in shear strength, making it more resistant to racking in walls.
Durability: OSB vs Plywood Sheathing
When it comes to durability, OSB is known for its impressive load-bearing capacity. It’s particularly good for subfloors and roofing where heavy loads are common. However, plywood tends to outperform OSB when it comes to long-term durability in moisture-prone areas.
OSB Durability
Because of its density, OSB can take on heavy weights without bending or warping, but it does have a drawback when exposed to moisture. OSB tends to swell along the edges when wet, and it doesn’t return to its original shape once it dries. That means if you’re using it in an area prone to moisture, like a bathroom floor, you may need to take extra precautions.
Plywood Durability
Plywood fares better than OSB in wet conditions. Its layers allow it to absorb and release moisture more evenly, making it less likely to warp or swell. For exterior applications where water exposure is a concern, plywood might be a safer bet.
Moisture Resistance
Moisture is one of the key concerns when comparing OSB and plywood sheathing. While both materials are engineered for structural use, they behave differently in wet conditions.
- OSB can absorb moisture quickly and, once swollen, doesn’t easily shrink back. This is something I learned firsthand while working on my garage roofing project. After a week of heavy rain, the OSB sheets had swollen at the edges, making it harder to lay shingles smoothly.
- Plywood, on the other hand, resists moisture better because of its cross-laminated structure. While it can still warp over time if not properly sealed, it typically handles moisture exposure much better than OSB.
Cost Comparison
Cost is often a deciding factor in many projects, and this is where OSB really shines. On average, OSB is significantly cheaper than plywood, which is one reason it’s widely used in construction.
When I was building an outdoor shed, I opted for OSB due to the cost savings. It was more affordable and allowed me to stay within budget, even though I knew I’d have to take extra precautions to protect it from the elements.
However, if you need long-term durability and better moisture resistance, investing in plywood may be worth the extra cost.
Weight and Ease of Installation
When it comes to handling, OSB is typically heavier than plywood. This added weight can make installation a bit more labor-intensive, especially if you’re working alone. On the flip side, OSB’s uniformity (no knots or voids) makes it easier to cut and install without worrying about weak spots in the material.
Plywood, being lighter and easier to work with, is often preferred for DIY projects. If you’re working on something like a home renovation and need to carry and cut many sheets yourself, plywood might be a better option.
Energy Efficiency
Both OSB and plywood sheathing provide similar thermal performance when used in wall assemblies. Neither material contributes significantly to insulation, but both serve as a base for adding additional insulation layers, helping to improve the overall energy efficiency of a building.
Environmental Impact
In terms of environmental considerations, OSB is often seen as more eco-friendly. It is made from small, fast-growing trees, and manufacturers can utilize wood scraps and chips. This reduces waste and ensures a more sustainable production process. Plywood, on the other hand, requires larger trees, which can lead to more deforestation and higher resource consumption.
Common Applications for OSB
OSB is commonly used for:
- Roof sheathing
- Subfloors
- Wall sheathing
- Shed construction
- Temporary flooring in construction zones
Common Applications for Sheathing
Plywood sheathing is frequently used in:
- Exterior walls
- Roof decking
- Flooring
- High-moisture areas
- Cabinet and furniture making (due to its smooth finish)
Conclusion
Choosing between OSB and plywood sheathing ultimately depends on the specific needs of your project. OSB is more affordable and strong, making it a great choice for budget-conscious builders. However, plywood offers superior moisture resistance and durability in the long run. Both materials have their strengths and weaknesses, and the best choice will vary depending on your project’s location, budget, and environmental conditions.
FAQs
Which is more water-resistant, OSB or plywood?
Plywood is more water-resistant than OSB, especially in high-moisture environments.
Is OSB stronger than plywood?
In terms of density and shear strength, OSB can be stronger than plywood, but plywood performs better over time in moist conditions.
Can you use OSB for roofing?
Yes, OSB is commonly used for roof sheathing due to its strength and cost-effectiveness.
Why is OSB cheaper than plywood?
OSB is made from smaller, fast-growing trees and wood scraps, making its production more efficient and affordable.
Does plywood last longer than OSB?
In moisture-prone areas, plywood generally lasts longer than OSB due to its better moisture resistance.